Interpretive Summary: Although glyphosate is the most used and studied herbicide in the world, the available information is not enough to fully understand its mode of action. The molecular site of action of glyphosate is the enzyme 5-enolpyruvlyshikimate-3-phosphate synthase (EPSPS). It is the only known compound that significantly affects this enzyme. Transgenic, herbicide-resistant plants that have genes for glyphosate-resistant EPSPS from microorganisms are highly resistant to glyphosate, proving that it this is the critical target site. Inhibition of EPSPS leads to reduced levels of aromatic amino acids (tryptophan, tyrosine, and phenylalanine)
needed for protein, cell wall, and secondary plant product synthesis. Furthermore, inhibition of EPSPS causes deregulation of the shikimic acid pathway, leading to a general disruption of plant carbon metabolism. This latter process is poorly understood.

Technical Abstract:
Although glyphosate is the most used and studied herbicide in the world, the available information is not enough to fully understand its mode of action. The molecular site of action of glyphosate is the enzyme 5-enolpyruvlyshikimate-3-phosphate synthase (EPSPS). It is the only known compound that significantly affects this enzyme. Transgenic, herbicide-resistant plants that have genes for glyphosate-resistant EPSPS from microorganisms are highly resistant to glyphosate, proving that it this is the critical target site. Inhibition of EPSPS leads to reduced levels of aromatic amino acids (tryptophan, tyrosine, and phenylalanine)
needed for protein, cell wall, and secondary plant product synthesis. Furthermore, inhibition of EPSPS causes deregulation of the shikimic acid pathway, leading to a general disruption of plant carbon metabolism. This latter process is poorly understood.